An electromechanical system in one example measures a parameter. For example, the electromechanical system comprises a micro-electromechanical system (“MEMS”) gyroscope that measures a rotation. The gyroscope in one example comprises a pendulous sensor component, a dither drive component, and a pickoff sensor. The dither drive component operates along a dither drive axis to set the pendulous sensor component into oscillation. The pendulous sensor component reacts to the rotation. The pickoff sensor senses the reaction of the pendulous sensor component to the rotation and a restoring force is provided by servo control electronics to restore and maintain the pickoff sensor signal at null.
A large source of bias error in Coriolis based micro-electromechanical system gyroscopes is the instability and non-repeatability of a component of the quadrature servo rebalance signal that appears in phase with the angular rate rebalance due to a remodulation phase error. Misalignment between the dither drive axis and an acceleration sensitive axis of the pendulous sensor component results in forces acting on the pendulous sensor component in the micro-electromechanical system gyroscope that are in quadrature with the desired rotation induced Coriolis forces. The misalignment in one example is caused by a non-vertical deep reactive ion etching of a dither beam suspension of the dither drive component during fabrication. Changes in the misalignment or the phase of remodulation result in bias error. As one shortcoming, the quadrature introduced by the misalignment between the dither drive axis and the acceleration sensitive axis of the pendulous sensor component coupled with phase error in remodulation results in an increased bias error.
Thus, a need exists for a reduction of a quadrature introduced by misalignment in electromechanical systems.